Conventionally, when an abnormality occurs in a drive power controller of a vehicle, an excessive amount of an actual drive power of the vehicle with respect to a driver's requested drive power is controlled by a fail-safe control. The fail-safe control performs a fail-safe action by shutting down a drive system of the vehicle.
For example, a vehicle control system disclosed in a patent document 1 (i.e., Japanese Patent Laid-Open No. 2009-62998) stops or reduces the output of the power source when an actual acceleration of the vehicle differs from a driver's requested acceleration.
The system of the patent document 1 performs the fail-safe action, when a malfunction detection unit detects that the actual acceleration is greater than the requested acceleration. In such a configuration, when the actual acceleration returns to normal immediately after temporarily exceeding the requested acceleration, the fail-safe action may be unnecessarily performed. Similarly, when a misdetection of the greater-than-requested acceleration occurs due to a disturbance, noise, etc., the fail-safe action may also be unnecessarily performed. Such an unnecessarily performed fail-safe action may lead to a deterioration of vehicle functions which is undesirable.
Further, depending on the vehicle behavior at the time of performing a drive power in-excess determination or, more specifically, according to a travel safety related vehicle behavior at such moment, the necessity for performing the fail-safe action is not uniformly determined. For example, when the drive power in a rear-wheel drive vehicle is excessive, if the amount of brake depression by a driver is large (i.e., if the driver depresses the brake pedal too abruptly), vehicle spinning or wheelspin may be easily caused. Also, in other cases such as (i) a large steering input into the steering wheel, (ii) a high speed or high acceleration situation, (iii) a vehicle traveling on a slippery road, or the like, a degree of danger may increase to a relatively high level. As a result, the fail-safe action such as stopping or suppressing of the engine drive and/or the motor-generator drive of the vehicle may have to be performed very quickly. However, the disclosure of the patent document 1 is silent about changing the determination standards/criteria based on which the fail-safe action is performed according to a vehicle behavior.